June 18, 2009

Comparative noise study K-7 vs. K20D

Today, I found the time to shoot images from a K-7 and a K20D side by side. In this article, I will highlight the differences in noise between the two cameras.

This is particularly interesting because Pentax used a 2nd generation version of the sensor used in the K20D, a 14.6 MPixel APS-C sensor now famous for its beautiful images when used with an excellent lens.

I am not interested to compare the advances in the camera's built-in JPG engine and its noise reduction (NR) algorithms. I am sure they are significant. I am interested in the best quality I can get from the camera, i.e. from RAW.

Test methodology:

- Almost constant lighting, although not perfect (indirect sun light)
- Constant setup:
- My "special" 400% ISO test chart on a wall.
- Constant exposure at EV 9.
- Again, underexposed by ~ -0.7 EV to exhibit more visible noise (to make it "gray").
- Second image underexposed by ~ -1.7 EV (EV 10).
- Tripod, K-7 MLU and K20D 3s timer, both via remote control.
- Zeiss 50mm/1.4 at f/4.0, manually focussed using magnified live view. (The Zeiss 50 is sharper in the center at f/4.0 than f/5.6.)
- Focus series for a resolution test (pending).
- Late sun and wood floor made a nice 3900 Kelvin color temperature.
- Shot in RAW (K20D: PEF, K-7: DNG) and exported by Lightroom using default settings.


- No colors.
- Focus was only almost perfect in the noise test.
- Only one camera of each type tested.
- My camera is a preproduction unit (with final firmware) which may give slightly inferior results to a production camera. Therefore, subtle differences may not be significant.

-- Begin of update --
The interpretation as authorized by Pentax is as follows: Tests carried out with preproduction units and final firmware are allowed to be taken representative of final quality. There won't be a noticeable difference when just inspecting photographs. However, there may be numeric differences when tests are carried out by a quantitative lab test, and if so, in favour of the production cameras. Therefore and because I didn't publish test figures, this blog article must not be considered premature.
-- End of update --


All results are presented as 100% crops prepared for easy inspection here:

Resolution and Noise of K-7 vs. K20D

Please, have a look before joing my conclusion (note that you'll see snippets magnified by 15x!).


The noise from the K-7 and the K20D almost look the same. If there is a slight advantage, then it would go to the K20D. But the difference is so marginal that I say:

There is no significant difference in noise from black & white subjects in raw files from the K-7 and the K20D.

The K-7 produces excellent results up to ISO 1600, and ISO 6400 remains reserved for smaller image sizes. It is however remarkable how much detail is preserved in even ISO 6400!
This is what Pentax is known for: Details rule over noise!


  1. hmm...super idee, wenn man die entrauschungsfähigkeiten der beiden kameras vergleichen will einen RAW-konverter mit den eingebauten entrauschungsalgorithmen zu verwenden...

    probier das doch bitte nochmal mit out-of-cam-jpegs.

    das ergebnis des vergleichs der beiden kameras im RAW finde ich auf jeden fall schon mal sehr interessant

  2. Karsten, ich wollte die Entrauschungsfähigkeiten der beiden Kameras doch eben genau NICHT testen (3. Absatz im Blogartikel).


    For those interested in a comparison of in-camera JPG NR delivered by K-7, I recommend the good comparison carried out be Frank Feng Wei:

  3. It seems like the K-7 is getting a bit more details out of the scene (with a little more moire though). So probably a weaker AA filter. Other that that, I agree, it's quite usable for large prints up to iso 1600. It's a pity you probably don't have a Canon40D/50D or NikonD300 to further complement the comparison ^^ would be very useful. Good job though, keep up the good work.

  4. Using a 3900K light source is not a good idea IMO. The noise from the Red channel will dominate (and the blue channel is almost neglected). And using the late sun as the light source is also not a good idea neither as the colour temperature and lighting level change both so rapid so that the consistency of the test results will be affected.

    Consider using a fixed artificial light source at something from 5000K to 6500K.

  5. Very interesting, Falk. Thanks for posting.

    And I agre: details rule over noise.

  6. I disagree with your verdict. While chroma noise is similar, luminance noise, which is responsible for details in most scenes, is much better controlled on the K-7. Chroma noise can be dealt with in postprocessing with appropriate plugins, but if it's dealt with in-camera, it's usually at the expense of detail.

    I suspect a well-exposed shot at ISO6400 with the K-7, passed through Noise Ninja or such, will be more than adequate.

    I do see a difference, and the K-7's sensor is superior in my opinion.

    Thanks for the comparison, Falk!

  7. @RiceHigh, I agree with your comments. My test lacks technical perfection.

    However, to use a quote from Einstein, I tried to keep it as simple as possible, but no simpler. By the way, the sun wasn't too late and EV was constant (except for one shot as I discovered too late). ;)

    @Misere, I now looked at the samples in b&w. The noise then just becomes indistiguishable to my eyes. You may have better eyes, however ;)

  8. With kudos to Miserere, I might have said this instead
    "I posted a noise comparison with the K20D in 'my test report and blog' thread and basically found that the PRE-PRODUCTION Beta version K-7 and K20D have no significant difference in noise."

    I see I great difference in this point alone. Too bad all of the testing was not left to wait until production K-7's were out on the street.

  9. @nic, I have updated my blog article to take your concern into account. According to Pentax, it isn't required to modify statements in the way you suggested.

  10. What a usless test... you used two completely different lenses on each camera in an attempt to compare them.

    That's just dumb

  11. Why dont you move your ass and test it then moron

  12. Do you know if the RAW files from the K-7 and K20D are the same? I ask because I am considering purchase of a k-7, but the software that I use (PS CS3 and its associated Camera RAW and Aperture 2.x) supports the K20D but does not mention the K-7. Adobe has explicitly included support for the k-7 in PS CS4 and its associated Camera RAW, but I'd prefer to skip this version and wait for CS5 if possible.


  13. @Anonymous ... useless test... I verified that both lenses@f-stop outresolve the sensor by a large margin and therefore, the lenses didn't have an impact on results (almost). I could show you the respective other lens result but I had too few shots to compile the superresolved test images.

    The test is not useless. Thanks for having been worried ;)

  14. @Anonymous ... K-7 Raw files.

    The K-7 has two RAW formats, PEF and DNG. PS CS3 fully supports the DNG variant. Unlike K20D, the K-7 produces compressed DNG of same size as PEF and there is no reason anymore to use PEF on the K-7.

  15. Thanks for the RAW format information and also for the time you've taken to explore the Pentax cameras.


Please if posting anonymously, choose a nickname for your post. Thanks.